The present invention relates to a fixing unit for fixing a toner image onto a print material, and to a lamp holder, a lamp cartridge using the lamp holder and a fixing unit using the lamp holder.
As fixing units of a printer, typical of a laser printer, a copier machine and the like, there is known a fixing unit in which print material holding a toner image is heated and pressed while it is being transferred between a heating roller and a pressing roller to fix the toner image onto the print material. Lamps operating as a heat source are located inside of the heating roller, and in general, the number of the lamps placed inside the heating roller is increased as the printing speed of the printer is increased.
In the use of such a heating roller having a plurality of lamps, when the heating roller is exchanged due to, for example, the expiration of the lifetime of the heating roller, the roller is replaced by a new heating roller by removing the lamps one by one and then removing the heating roller from the fixing unit. Therefore, the amount of work required to detach and attach the lamps from and to the heating roller is in proportion to the number of lamps, and, accordingly, the work efficiency of this maintenance task has been low.
A structure to solve such a problem is proposed, for example, in published Japanese PCT international publication for patent application No.5-504633(1997). According to Japanese PCT international publication for patent application No.5-504633, the disclosed structure is designed such that the lamps can be pulled off from the back side of the fixing unit in a state in which the heating roller remains attached to the fixing unit.
lamp used in a fixing unit of this kind has a long and slender shape with a diameter about 10 mm and a length above 600 mm. In the case of the structure disclosed in Japanese PCT international publication for patent application No.5-504633, because the attaching and removing of the lamps to and from the heating roller is performed in a state in which the lamps are exposed, there has been a problem in that the lamp surface is scratched or the lamps are broken due to contact between the lamps and the edge of the heating roller or between the lamps and other parts, when the lamps are being attached to or removed from the heating roller.
An object of the present invention is to make the work of replacing the fixing lamps easy and to shorten the non-operational time period of the printer associated with the maintenance work.
Further, another object of the present invention is to hold the fixing lamps attached inside the heating roller in a correct position without displacement in the heating roller.
The above object can be attained by a fixing unit comprising a heating roller having a plurality of fixing lamps inside; and a pressing roller arranged so as to be capable of pressing against the heating roller, a print material having a toner image being transferred between said heating roller and the pressing roller to fix the toner image onto the print material, wherein the fixing lamps are formed as a lamp cartridge which comprises a first lamp holder for holding one end of the fixing lamps; a second lamp holder for holding the other end of the fixing lamps; and a protective member holding portion for holding a lamp protective member which is attached to the heating roller depending on necessity. The protective member holding portion is arranged around a region where the lamp holding member is placed, whereby all of the plurality of fixing lamps are capable of being attached to and removed from the heating roller together from one end of the heating roller.